Elastic Softening of (Mg0.8Fe0.2)O Ferropericlase Across the Iron Spin Crossover Measured at Seismic Frequencies
Elastic Softening of (Mg0.8Fe0.2)O Ferropericlase Across the Iron Spin Crossover Measured at Seismic Frequencies
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DOI：
10.1029/2018gl077982
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发表时间：
2018-07
影响因子：
5.2
通讯作者：
H. Marquardt;J. Buchen;A. Méndez;A. Kurnosov;M. Wendt;A. Rothkirch;D. Pennicard;H. Liermann
中科院分区：
文献类型：
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作者：
H. Marquardt;J. Buchen;A. Méndez;A. Kurnosov;M. Wendt;A. Rothkirch;D. Pennicard;H. Liermann
我们通过一种新的实验方法，实验测定了（Mg0.8Fe0.2）O铁方镁石在铁自旋跃迁和低自旋相的体积模量。在我们的测量中，我们通过采用压电驱动的动态金刚石压砧单元来模拟压缩地震波（P波）通过我们的样品的传播，该压砧单元允许在地震频率下振荡压力。在压力振荡期间，每5-50 ms连续收集一次X射线衍射图像。根据不同压力下的这些数据直接计算体积模量。我们的实验表明，在整个自旋交叉过程中，体积模量明显软化，支持以前在非常高的频率下进行的单晶测量和计算。我们的结果与以前收集的数据（Mg，Fe）O与较低的铁含量的比较表明，软化的幅度强烈依赖于铁含量。我们在地震频率的实验证实，铁自旋交叉显着影响地球下地幔的地震纵波速度与横波速度之比。
We experimentally determined the bulk modulus of (Mg0.8Fe0.2)O ferropericlase across the iron spin transition and in the low‐spin phase by employing a new experimental approach. In our measurements, we simulate the propagation of a compressional seismic wave (P wave) through our sample by employing a piezo‐driven dynamic diamond anvil cell that allows to oscillate pressure at seismic frequencies. During pressure oscillations, X‐ray diffraction images were continuously collected every 5–50 ms. The bulk modulus is directly calculated from these data at different pressures. Our experiments show a pronounced softening of the bulk modulus throughout the spin crossover, supporting previous single‐crystal measurements at very high frequencies and computations. Comparison of our results to previous data collected on (Mg,Fe)O with lower iron contents shows that the magnitude of softening strongly depends on iron content. Our experiments at seismic frequencies confirm that the iron spin crossover markedly affects the ratio of seismic compressional to shear wave velocities in Earth's lower mantle.